This invention relates to solid-fluid contacting. In particular, it relates to solid-fluid contacting carried out in a batch system wherein solid particles are contacted with at least two batches of fluid.
In many batch processes requiring contacting fluid with solid particles, some of the solid particles remain active after processing of the first batch or even after processing several batches; consequently, it is often advantageous to reuse these solid particles in subsequent batches. The majority of solid-fluid contacting operations are most efficient when the contact surface, between the fluid and the solid particles, is at its maximum and when the solid particles are dispersed uniformly throughout the fluid. Since the maximum contact surface is achieved by using solid particles of smallest possible sizes, a difficulty arises in removing such small sized particles uniformly dispersed throughout the fluid. One way to accomplish removal is to withdraw the fluid together with the solid particles carried therein, then outside the vessel separate solids from the fluid. Another method is to provide a filter or a screen in the exit conduit of the vessel to allow the fluid but not the solid portion of the mixture to leave the vessel. This approach is marred by one difficulty -- the solid particles become retained by or embedded in the screen or filter. The retained particles become unavailable for contacting with subsequent batches of feed and they gradually accumulate on the filter causing the filter to become plugged to such an extent that it must be removed and replaced, disrupting the continuity of the batching process and resulting in increasing the cost of the process.
The present invention obviates some of the problems in batch solid-fluid contacting processes by providing an improved method and apparatus for carrying out such contacting.
Thus, one object of the invention is to provide a more efficient solid-fluid contacting process and apparatus.
Another object of the invention is to make the processes for contacting fluid with solid particles more efficient by eliminating interruptions due to cleaning of filter means.
Still another object of the invention is to reuse solid particles contacted with one batch of fluid without additional steps of separating the solid particles from the fluid outside the vessel and replacing them into the vessel for processing of subsequent batches.
A still further object of the invention is to reduce the operational and maintenance costs of the solid-fluid contacting processes in which some of the solid particles are reuseable.
Still another object of the invention is to make it economically possible to reuse some of the solids in the batch solid-fluid contacting processes.
A still further object of the invention is to simplify the batch processes for contacting of solids with fluids in which at least some solids are reuseable and to reduce the size and complexity of the equipment.
Still another object of the invention is to provide an improved batch process for reacting fluids in the presence of a solid catalyst, where the products are withdrawn from the reaction zone but the catalyst is retained therein for processing a subsequent batch of feed.
Other objects of the invention will become apparent to those skilled in the art upon studying this specification and the appended claims.